The present invention relates to a pressurized fluent product dispensing container, particularly an aerosol container, and more particularly relates to the cover of the container, and specifically to a cover which resists deformation due to the internal pressure in the aerosol container.
Various fluent materials may be stored in a pressurized dispensing container having a cover with a dispensing nozzle for the fluent material. Various fluent materials, including pressurized gases, sprayable liquids under pressure, flowable liquids under pressure, liquids mixed with propellants and liquids under pressure within a container but not mixed with the propellant (in barrier pack containers, for example) are stored in a container and are dispensed through a nozzle supported in the cover of a pressurized container. The invention hereof is applicable to the cover on any type of pressurized container with a nozzle for dispensing fluent material. The invention is particularly described with reference to an aerosol container wherein a dispensable liquid is mixed with a volatile propellant in the container under pressure. Upon actuation of the container nozzle, a mixture of the volatile propellant, which exits the nozzle in liquid and/or gaseous form, and of the liquid contents of the container, which together with the expanding propellant forms a spray or a mist as it exits the nozzle under pressure, are dispensed through the container nozzle. In certain cases, the propellant does not mix with the liquid, but its pressure forces the does not mix with the liquid, but its pressure forces the liquid out and the propellant in gaseous form can also mix with the liquid in the nozzle, if the nozzle has a vapor tap.
The essential components of a typical aerosol spray container are the can or container which has an open top end, a cover or lid that is attached over the open end and a nozzle supported in the cover and communicating in the container for dispensing the container contents through the nozzle when the nozzle is actuated.
In order to dispense the contents of an aerosol spray container with sufficient force and to dispense the entire dispensable contents of the container, the conventional practice has been to increase the gas pressure of the propellant material in the container to a high enough level. Higher internal pressures require both the can walls and the cover to be sufficiently stiff and strong to contain the elevated pressure without deforming or bursting, especially under the stresses applied during shipping and handling and storage and particularly to withstand the elevated internal gas pressure developed in a heated environment, as could occur on a hot summer day in an unventilated storage location. The conventional way of strengthening the can and/or the cover on the can is to make it out of a stiff metal and usually also to make the can wall and the cover of thick enough material that it will neither deform nor burst under the elevated pressures that might be experienced under extreme heat or other unusual environmental conditions. However, thicker can walls and covers have several drawbacks. They are heavier in weight, more costly due to the quantity of materials to be used, more expensive to manufacture, and so stiff as to not be easily deformed or crushed for disposal or recycling. Further, transportation of heavier containers also requires more energy and is typically more expensive than transportation of lighter weight containers.
The inventors hereof recently made inventions which are contrary to the conventional practice, discussed above. Thy have developed a container having a thin walled body, which being cylindrical and seamless is very strong. This thin walled body is used in conjunction with a bottom which can be of much thicker wall construction, and is therefore also very strong. The propellant used in the container gives the container its rigidity, as well as acting as a propellant. Container rigidity is maintained with a very low residual pressure, i.e., after all the product has been dispensed. As a result, the wall of the container body could be made sufficiently thin enough that the unpressurized or emptied container could be crushed even by finger pressure. Such crushability was virtually unknown with prior aerosol dispensing containers. The inventors hereof use the internal pressure of the propellant and fluent material in the container to help maintain the undeformed shape of the container. But when the container is emptied of dispensable content, it can be crushed by finger pressure. This container concept is embodied both in an aerosol spray can in U.S. Pat. No. 5,211,317 and/or in a barrier type dispensing can in U.S. Pat. No. 4,171,757. Both patents are incorporated herein by reference for their teachings of thin walled, crushable cans, the benefits of thin walled cans and the environmental problems of thicker walled cans. However, even the thin walled cans have to this time been supplied with thicker, heavier covers to prevent the covers from deforming under the elevated pressures that may develop within the container.
A typical cover or lid for an aerosol container is not essentially flat or planar across the cover. In a cross section through a cover, it is crimped at its peripheral margin to the open end of the container; has a countersunk recess formed in the cover and projecting into the container and located adjacent the peripheral crimp; radially inward of the recess has a rounded, generally convex dome; and toward the center of the cover, the dome terminates at a stiffening rib where the dispensing nozzle penetrates through and is supported in the cover. The bottom of the countersunk recess in the cover is the weakest point in the cover and the most susceptible to deformation because of excessive pressure within the aerosol container.
If the metal or other material used for the cover of an aerosol container is too thin for the required pressures, the cover, which is already of a shape selected for strength, would deform and rise further out of the container, pulling up the metal from the outer side wall of the countersunk recess at the periphery of the cover and the cover would then be permanently deformed. When such deformation occurs, the outer side wall and bottom of the recess tend to unfold upwardly along with the rising cover until the recess is eliminated or substantially eliminated. A cover which deforms during testing or transportation is illegal, as well as being aesthetically unpleasant. Also, it may improperly position the nozzle with respect to the container and its contents and it may promote a leak from the container at the periphery of the cover.
Typically, the lid or cover of a container can usually cost as much money to make as the body of the container. It would be desirable to make the lid cheaper, for instance by making it as thin as possible for the particular pressures required. Further, a thinner cover is lighter in weight, and more easily deformed for discarding or recycling. If one of the inventors' thinned wall, easily deformed, recyclable containers were to have a stiff nondeformable cover, the disposability and recyclability of the container would be reduced. It is beneficial to have a lid or cover on the container with deformability similar to that of the container. In this manner, various governments' requirements can be met while maintaining low cost and desirable environmental properties.